Sri Lanka's military says rebels have ambushed a navy bus in the east of the country, wounding 12 sailors and sparking a gunbattle in which two civilians also died.

Officials blame Tamil rebels for Tuesday's attack in Trincomalee. They say the rebels set off a fragmentation mine as the navy bus passed by, and then opened fire on the bus with small arms. Officials say the sailors shot back, and two civilians were killed in the crossfire.

Sri Lanka's government says at least 69 security personnel have been killed by rebels since early December. The violence has severely strained a ceasefire signed by both sides in 2002.